The Viktor Leonov CCB-175 was moored to a pier in Old Havana where cruise ships often dock, but its arrival was not announced by Cuban authorities.

The Vishnya or Meridian-class intelligence ship, which has a crew of around 200, went into service in the Black Sea in 1988 before it was transferred seven years later to the northern fleet, according to Russian media.

The vessel previously docked in Havana in February and March last year, staying there for a few days. Those visits were also unannounced.

The highest-level US delegation to visit Havana since 1980 arrives Wednesday for two days of talks aimed at normalizing diplomatic and immigration relations between the former Cold War foes.